Synthetic studies on glycosphingolipids from protostomia phyla: Synthesis of amphoteric glycolipid analogues from the porcine nematode, Ascaris suum

A novel amphoteric glycosphingolipid, cholinephosphoryl-(→6)-β-D- GlcpNAc-(1→3)-β-D-Manp-(1→4)-β-D-Glcp-(1→)-Cer, isolated from the porcine parasitic nematode, Ascaris suum, may be expected to be involved in host-parasite interactions. This glycosphingolipid analogue containing octyl residue in place of ceramide was synthesized as follows: The key reaction of this synthetic procedure is the formation of a intramolecular aglycon delivery (IAD) approach for β-selective mannosylation. Then, a coupling of phosphocholine group at the position C-6″ of 16 was attempted using 2-chloro-2-oxo-1,3,2-dioxaphospholane, followed by reaction of the resulting cyclic phosphate intermediate with anhydrous trimethylamine to give 17. Subsequent debenzylation and debenzylidenation afforded target compound (2).